[MDEV-11923] Galera node does not resynchronize after rejoining the cluster Created: 2017-01-27  Updated: 2019-05-20  Resolved: 2019-05-20

Status: Closed
Project: MariaDB Server
Component/s: Galera
Affects Version/s: 10.1.21
Fix Version/s: N/A

Type: Bug Priority: Major
Reporter: Michaël de groot Assignee: Jan Lindström (Inactive)
Resolution: Not a Bug Votes: 0
Labels: None


 Description   

Hi!

I don't know if this behaviour is intentional but I think it is faulty behaviour. If we disable wsrep_on on a Galera node, restart it, perform changes and then rejoin it to the cluster, the changes are not overwritten or replicated.

Steps to reproduce:
1. Create a galera cluser with 2 or moren odes
2. Shutdown 1 node
3. Change that node's configuration to wsrep_on=0
4. Start the node, insert a row into a table
5. Stop the node, wsrep_on = 1, start the node
6. Delete the changes inserted in step 4
7. Observer the other nodes go down

In my opinion, the server should remove / invalidate grastate.dat when it is started without galera being enabled. Otherwise, if the joining node has different data, this could result in very bad results:

  • The other nodes would go down when this node receives changes on the incorrect data
  • This node would go down (and still overwrite these faulty changes) if the other nodes cause for example a primary or unique key conflict, causing an unexpected outage

Thanks!
Michaël



 Comments   
Comment by Jan Lindström (Inactive) [ 2019-05-20 ]

You are intentionally bringing cluster to inconsistent state. On Galera 3 there is not yet any inconsistency voting where majority of the nodes would vote what is actually the correct state of the database.

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